1. Field of the Invention
The present invention relates to an agent for treating an exhaust gas containing a metal hydride gas and/or an organometallic gas, and a process of treating the exhaust gas using the agent. More particularly, the present invention relates to a dry gas treating agent, which is used to remove an exhaust gas containing a low concentration of a metal hydride gas and an organometallic gas by passing it through the treating agent containing a solid metal oxide and a solid metal carbonate as a main component, and a treating process thereof.
2. Description of the Related Art
Various gases has been used as a gas for production of a semiconductor and called as a metal hydride gas such as SiH.sub.4, Si.sub.2 H.sub.6, GeH.sub.4, PH.sub.3, and AsH.sub.3, or an organosilane. Among them, the organosilane gas such as methylsilane, ethylsilane, and phenylsilane has attracted special interest recently because it exerts a specific performance adequate for a dry photoresist agent in the production of a semiconductor device, or a low-dielectric material for formation of a layer insulation film.
However, any of these gases is drastically dangerous because of high toxicity, reactivity and spontaneous ignition property. Since these gases have high toxicity, e.g. severe irritation to the respiratory organ upon respiration, we can foresee a harmful influence on the human body and natural environment if these gases are released out of the system in a high concentration. Therefore, it is a natural responsibility for persons in charge to reduce the concentration of the organosilane gas contained in the exhaust gas from its production process and after the use semiconductor industry in view of retention of good working atmosphere and prevention of destruction of the natural environment.
Accordingly, it is required to make the exhaust gas harmless,before released in an air, and a dry treating agent made of a solid metal oxide (Examined Patent Publication (KOKOKU) No. 4-19886) or a solid metal carbonate (Unexamined Patent Publication (KOKAI) Nos. 59-160535 and 8-192024) and a treating process using the same have hitherto been suggested.
In case where these components are contained in the exhaust gas in a high concentration, heat is generated by the reaction with the treating agent made of the solid metal oxide and a sufficient treatment can be conducted by the successive reaction. However, in case of the exhaust gas having a comparatively low concentration, a sufficient treatment cannot be conducted because of poor reactivity.
In case of the treating agent made of the solid metal carbonate, a sufficient reaction takes place even in case of the exhaust gas having a comparatively low concentration, but the amount of the exhaust gas to be treated per volume of this treating agent is poor. If this treating agent is brought into contact with air after passing the exhaust gas through it, high temperature heat is generated, resulting in poor handling.
In a conventional process, it was considered to be effective to supply the exhaust gas while heating a packed bed so as to enhance the capability of treating the exhaust gas. However, this heating process requires high energy cost and gives rise to generation of particles from a heat insulating material in the vicinity of a heater and, therefore, it was a problem in a semiconductor factory where particles should be avoided.